The present invention relates to a throw-away burnishing tool for burnishing an outside diameter of a workpiece and a throw-away burnishing tool for burnishing an inside diameter of a workpiece.
Conventionally, for burnishing the surface of hardened steel having a hardness of HRC 40 or more and when burnishing the surface of a stainless steel material, burnishing tools using diamond in place of rollers are known.
FIGS. 4A through 4C show a conventional throw-away burnishing tool 30 using diamond, wherein FIG. 4A is a plan view, FIG. 4B is an enlarged plan view of an S-portion of FIG. 4A, and FIG. 4C is a sectional view along the line R-R of FIG. 4B. This kind of throw-away burnishing tool for an outside diameter is known; for example, from an IMS burnishing tool type BNN manufactured by IMS Co., Ltd. See IMS Burnishing Catalogue distributed by General distributor Nitmac.
Tool holders have various sizes, and the maximum throw-away burnishing tool 30 is 25 mm×25 mm in cross section (width×height) and 160 mm in total length.
As shown in FIG. 4B, at a front-end portion of a tool holder 35, an attachment seat 35a for a tip holder 36 is provided, and to this attachment seat 35a, the tip holder 36 is fixed by a bolt 35b. This bolt 35b is inclined at 30°, and an attachment seat 36e for a tip holder 36 shown in FIG. 4C is also inclined at 30°.
In addition, a hole 36a inclined at 45° is bored in a left front-end portion of the tip holder 36, and a diamond tip 37 is inserted into this hole 36a and is fixed by a screw 36c. In addition, at a central portion of the tip holder 36, a roughly double-keyhole shaped groove 36b is formed, and by this groove 36b, only a section between a double-keyhole head portion and an outer circumferential surface 36d is integrally connected. In order to urge this tool holder 35 against the tip holder 36, elastic deformation of a connecting portion 36g is utilized.
As shown in FIG. 4C, the tip holder 36 is formed in a T-shape in a front view. The attachment seat 36e for the bolt 35b is inclined at approximately 30°, a notch is formed in a U-shape in a bolt through-hole 36f, and only by loosening the bolt 35b, the tip holder 36 can be replaced, and by tightening the same, the tip holder 36 is pressed against the shoulders of the attachment seat 35a and is fixed thereto.
In addition, as shown in FIG. 4B, an aspherically formed diamond 37a is embedded in a front-end portion of the diamond tip 37, and the diamond tip 37 is formed with clearance angles α and β of 5° from its surface.
In addition, a height to the center of the diamond tip 37 is 25 mm, which is the same as the height of the tool holder 35, as shown in FIG. 4C.
However, since the conventional throw-away burnishing tool 30 for an outside diameter has employed an urging method by an elastic deformation of the connecting portion 36g provided at the tip holder 36, when a pressing force which the diamond tip 37 imparts to a workpiece is changed in magnitude, the diamond tip 37 is changed in posture. Therefore, there are several problems, such that the machining direction is not fixed, that the pressing force is not changed by changing an urging force during machining, that it is difficult to satisfy Hooke's law, namely, a linear proportional relationship between displacement and urging force, and that an accurate adjustment for the urging force is not made.